Future wireless communications systems are operating at ever higher carrier frequencies in a quest to find greater bandwidth and less interference. These wireless communications systems may operate at frequencies of 6 GHz and above, which are referred to herein as millimeter wave (mmWave) frequencies. However, operating at the mmWave frequencies also present challenges, including: greater pathloss compared to lower frequency bands (on the order of 10-20 dB additional loss); fewer user multi-path with link fragility becoming a major problem for continuous coverage; and significant increase in digital signal processing due to the much greater available bandwidth (especially for user equipments (UEs)).
A variety of techniques have been proposed to combat the challenges, including: beamforming with large array gain (at both the terminal devices and access nodes) to overcome pathloss; simultaneous connectivity with multiple access nodes to overcome link fragility (implying a dense deployment that presents an opportunity for in-band backhauling among the access nodes while requiring an air interface that is flexible without undue complexity); and simplified signal processing for communicating devices, especially the terminal devices.